Methods of making a lignocellulose product and products resulting therefrom



Patented May 8, 1962 thee Iowa No Drawing. Filed Oct. 22, 1958, Ser. No. 768,832

2 Claims. (Cl. 106-463) This invention relates to methods of making a lignocellulose product and to the products resulting therefrom.

This application is a continuation-in-part of my copending application Serial No. 764,232, filed September 30, 1958, now Patent 2,984,578, dated May 16, 1961.

It is an object of this invention to provide an improved method of making a moldable composition comprising reacting an essentially dry mixture including comminuted lignocellulose and a reactant of the class consisting of acids, inorganic sulfates, inorganic sulfites, inorganic bisulfites, inorganic sulfides, inorganic phosphates, inorganic nitrates, inorganic halides, sodium salts, inorganic halogens, organic oils, organic alcohols and polyols, organic aldehydes and ketones, phenols, organic bases and nitrogen compounds, organic monomers and unsaturated compounds and resins.

Another object of this invention is to provide such a method wherein the amount of reactant is about 0. 130.0% by weight of the lignocellulose, the reaction is conducted in an atmosphere of steam at about 275- 475 F. ata pressure of about 50450 pounds per square inch gauge, and for about 460 minutes.

A further object of the invention is to provide lignocellulose products prepared by the above methods.

Other objects and advantages of the invention will be apparent from the following description of several embodiments of the invention.

An important advantage of the invention appears to be the controlling of the reaction so that the alpha cellulose is reduced in molecular size sufficiently to prevent swelling of subsequently fabricated products but not to the extent that toughness of fibre is lost. This latter occurs under drastic degradation and starts to become quite serious when approximately 25% of the lignocellulose has been lost as either gaseous or soluble byproducts.

Another advantage appears to be the plasticization of the lignin component during the controlled cellulose degradation so that the lignin can subsequently be made to flow and function as a binder between the comminuted lignocellulose particles.

Another advantage is the provision of a relatively dry system so that high capacity for the process of, for example wood waste is attained. This is not possible in a Wet process such as ordinarily found in a pulping process in which the reactor is charged with approximately 90% water which takes up space as well as requires the addition of large amounts of energy to bring the reaction medium to the proper temperature.

Another advantage is the contacting of lignocellulose or dry mixes of lignocellulose and other ingredients under superatmospheric pressure with a vapor or combination of vapors functioning both as a heat transfer medium and as a reactant.

In the method of this invention an essentially dry mixture including comminuted lignocellulose and a reactant is reacted as by heating while confining the lignicellulose and the reactant under superatmospheric pressure as in an autoclave. During the reaction the lignocellulose bond is apparently broken and the lignin is released to operate as a binder.

It appears that the hemi-celluloses are the primary constituents of the lignocellulose which are attacked by hydrolysis, but that under the high pressure and temperature of this invention a portion of the hydrolysates are further converted to higher molecular weight materials which can function as plasticizers for the autoclave product when it is molded. At the same time a controlled degradation of the alpha cellulose is carried out to the extent that the desired degree of moisture stability is obtained in the molded or extruded products without an unnecessary loss of toughness. These actions are believed to occur although they have not been absolutely proven.

The methods of this invention may be carried out batchwise in an autoclave or a sealed press or continuously in a continuous contactor.

The lignocellulose which appears dry to the touch actually contains up to about 30% water before the reaction begins.

The lignocellulose which may be used in this invention includes Wood as well as other lignocellulosic vegetable materials. The lignocellulose is finely divided so that the particles are preferably not more than 20 mesh in size as measured by a standard screen although smaller sizes are preferred.

During the reaction which takes place in a confined atmosphere under superatmospheric pressure various reaction products are produced although the exact nature of the reaction is not understood. It appears that the reaction products are either inert so that the product itself is inert, have a binding action such as is true of the lignin produced, are gaseous by-products, or are polymerized. By hydrolyzing and partially removing, or polymerizing the herni-celluloses to lignin type materials, the ratio of lignin and others binders to the alpha cellulose is increased so that the general nature of the lignocel lulose mixture is drastically changed.

The high pressure method of this invention has a number of advantages that are not possible with reactions taking place at ordinary pressures and in an unconfined state. In the preferred process, steam is introduced into the autoclave both for heating purposes and to supply moisture for the reaction. In the high pressure method of this invention heat transfer is much more rapid so that in general a shorter reaction time is required. Furthermore, energy losses during the reaction are greatly reduced. In the ordinary reacting mixture these energy losses result from the release of volatile materials such as water vapor, gaseous reaction lay-products and the like. As the reaction here takes place in a confined atmosphere, no such losses occur to any material degree. Furthermore, the energy supplied by the steam or vapor is utilized to heat only the lignocellulose with its approximately normal moisture content in contrast to pulping type reactions where large quantities of water are present, requiring far greater expenditures of energy.

Another important advantage of this process is the close control that is obtained over the reaction. Thus the temperature of the reacting mass, and hence the rate of reaction, can be easily raised or lowered by controlling the rate of flow, pressure and the temperature of the heat transfer medium which may be steam, oil vapor, or other high temperature fluids. Reactions may easily be stopped by flashing the heat transfer medium from the autoclave since the large energy loss on expansion cools the reacting mass below the incipient reaction point. During the practice of the process the reacting mixture may be confined in a jacketed vessel with the heating medium introduced to the chambers in the quantity and temperature desired.

A very important advantage of the invention is that volatile reactants may be used as the reacting mass is in a confined space. Volatile reactants are impossible, of course, when the reacting mass is in the open. As a result of the rapid heat transfer achieved by this invention and the penetration of volatile reactants the reaction not only proceeds to completion in a much shorter time but the final product tends to be more uniform than where the reactants are heated such as in an ordinary process that depends upon surface temperature diiferentials.

Tests have shown that the confining of the reacting mass in the autoclave not only causes retention of the by-products of reaction within the mass even when the by-products are gaseous but also causes polymerization of all or a portion of these by-products, even some that are gaseous. In so-called wet processes large quantities of the by-products of reaction go into solution and are lost.

Another advantage of the invention is that the volatile by-products are easily collected and removed at low cost for later use where desired or to prevent the creation of a nuisance.

Where volatile reactants are used no mechanical mixing of the ingredients is required. This results in a considerable saving in time, labor and other factors. Thus, in these instances, it is only necessary to charge the reactor with the lignocellulose and introduce the volatile materials into the reactor under superatmospheric pressure. In addition, if desired, the reactants can be changed or modified during the course of a run. This is not possible to such a degree in a wet process where the charge generally contains less than 50% of lignocellulose, and addition of reactants would in many cases cause prohibitive amounts to go into solution.

A further advantage of utilizing the vapor process is that the volatile content of the reaction product which is primarily moisture can be controlled. By using superheated steam with a sufiicient degree of superheat, products on the order of 1% or lower volatile content can be obtained. Under normal conditions, to degrees of superheat at 300 pounds per square inch steam pressure will produce a product of 3-5% Volatile content. Thus the expensive drying step connected with wet processes can be avoided.

Because of rapid penetration of reactants under high pressure, larger sized particles can be charged to the autoclave than would ordinarily be used, and a savings in size reduction cost made as a result of lower power requirements to reduce the treated material in comparison with raw lignocellulose.

In addition, where fiat stock of preformed material is being made as in a sealed press, the products can be made much thicker and more uniform than in an ordinary press which depends upon high platen temperature for heat transfer, and in many cases requires almost prohibitive cycle times.

The reactant is thoroughly mixed with the finely divided lignocellulose and then heated at a temperature and pressure and for a time sulficient to react at least a portion and preferably a major portion of the reactant or reactants with the lignocellulose.

In the preferred process the temperature of the steam is between about 275-475 F. and the pressure is between about 50550 pounds per square inch gauge. The amount of reactant is preferably between about 0.1- 30.1% by weight of the lignocellulose. Where strong reactants such as strong inorganic acids are utilized lower pressures may be used, generally preferably between about 50-300 pounds per square inch. When others such as neutral compounds and alkaline materials are reacted with the lignocellulose, high pressures of between about 200-500 p.s.i. are preferably used.

In the practice of this invention where solid reactants are used, they are preferably finely divided, and blended with the lignocellulose such as in a mixer, prior to the reaction in the autoclave. When liquids are used, they may be diluted with water or other solvents so that they will be thoroughly dispersed throughout the mass of lignocellulose. Preferably an amount of solution up to about 20% of the weight of the lignocellulose is utilized. If both solids and liquids are added, the solid is preferably blended with the lignocellulose before the addition of the liquid.

EXAMPLE 1 To 500 grams of 20 mesh, hammer-milled Ponderosa pine containing only its normal moisture content of approximately 6% was added grams of a 5% aqueous phosphoric acid solution. Based on the weight of the lignocellulose, the amount of solution was approximately 20%, and the phosphoric acid was 1%. The mixture was ball-milled for /2 hour to obtain a uniform dispersion of the phosphoric acid throughout the mass. This composition was then placed in a heated autoclave and steam was admitted until the pressure was 200 pounds per square inch gauge and the temperature was approximately 400 F. The autoclave was held under these conditions for 20 minutes, and then the steam was rapidly flashed 01f. During the course of the run, the pressure was maintained at 200 psi. by venting off the excess pressure caused by volatile reaction by-products. The granular reaction product which has been cooled below the incipient reaction point by the rapid steam flash-off was removed from the autoclave, and all particles which had consolidated were thoroughly broken up. The moisture or volatile content of this material was approximately 10%.

In substantially the same manner as specified in Example 1, reaction products of lignocellulose and hydrochloric, sulfuric and nitric acids were prepared. The following table sets forth the quantity of acid used, based on the weight of the lignocellulose, the reaction time, and autoclave conditions maintained during the run.

When inorganic acids are reacted with the lignocellulose, they are preferably added in an amount between about 0.5-10.0% of the Weight of the lignocellulose.

Inorganic sulfates, sulfites, bisulfites and sulfides may also be reacted with lignocellulose in the presence of moisture such as steam in the same manner as Example 1. Generally the autoclave pressure is preferably somewhat higher than with the acid and is usually between about 200-400 p.s.i., although it is not necessarily limited to this range. When these materials are used, the preferred quantity is between about 115% based on the weight of the lignocellulose. They are preferably added to the lignocellulose in the form of an aqueous solution, unless they are relatively insoluble, and then they are preferably used as finely divided solids so that they will be uniformly distributed throughout the mass of lignocellulose.

Table II below lists a number of representative reac- 5 tions utilizing the sulfates, sulfites, bisulfites and sulfides with lignocellulose,

Table II Reac- Autoclave Other 1 tion Ex. Reactant additives time,

min. temp Press,

F. psi.

10... 2% ammonium sulfate.... 20 440 11--. 2% calcium sulfate.- 20 440 12.-- 1% zinc sulfate..-- 25 400 13-.-- 2% zinc sulfate.... 20 440 14--- 2% ferrous sulfate- 20 400 15--- --d 20 440 16--- 2% ferric sulfate 20 440 17.-- 1% ferric sulfate--- 20 440 18..- 1% cupric sulfate.- 20 400 19--- 3% cupric sulfate. 10 440 20.-- 1 aluminum sulfate 20 440 21--- 2% aluminum sulfate-. 20 440 22--- 1% aluminum sulfate.. 20 400 23--. 2% aluminum sulfate--- 20 440 24--. 1% aluminum sulfate. hgnm-- 20 400 25. .do 5% phenol 20 400 residue. 26... 2% sodium sulfite None 25 440 27.-. .-do 6% sulfur 25 440 28..- 2% sodium bisulfite None 30 460 29--. 2% ammonium bisulfite-. -d -30 460 30... 2% aluminum bisulfite-- 20 440 31-.. 3% sodium sulfide--... 30 460 :32--- 3% ammonium sulfide. 20 440 33.-. 5%fighosphorus pcntasnl- 20 440 All of the percentages given in the above table are based on the weight of the lignocellulose.

In addition to the previous examples, inorganic phosphates, nitrates and halides, halogens, sodium salts and zinc dust have been reacted with lignocellulose in the same manner as given in Example 1. These materials are preferably reacted in a pressure range of between about 200-450 p .s.i. They are preferably added in an amount equal to between about 1-15% by weight of the lignocellulose. Table III below lists a number of representative reactions along with the autoclave conditions under which these classes of reactants have been utilized.

Table 111 Autoclave Reaction Ex. Rcactant time,

mm, Temp., Press,

F. p.s.1.

34..-. 2% sodium phosphate 25 440 300 35..-- 2% calcium phosphate plus 5% Vinsol. 20 440 300 36..-. 2% aluminum phosphate 20 4-10 300 37-..- 2% calcium nitrate.... 20 440 300 38..-. 2% zinc nitrate 20 440 500 39..-. 2% aluminum nitrate- 5 440 300 40---- 1% iodine 20 400 200 41...- 2% iodine plus 5% Vinsol 20 440 300 42.--- psi. chlorine 10 425 158 43..-. 35 p.s.i. chlorine plus 10% sulfur. 10 428 198 44.... 2% calcium iodide 440 300 45-... 2% zinc iodide 20 440 300 '46...- 2% calcium bromide..- 20 440 300 47...- 2% zinc bromide 20 440 300 48...- 2% sodium carbonate 440 300 49..-. 3% sodium silicate 25 440 300 50.... 2% sodium perborate 25 440 300 51...- 2% sodium benzcnesulfonate 25 440 300 52...- 3% sodium henzoate 25 440 300 53..-. 5% zinc dust 25 440 300 53...- 5% zinc dust 25 440 300 All of the percentages in the above table are based on the weight of the lignocellulose. The chlorine of the halogen group is quite reactive and in thi respect is similar to strong mineral acids. Therefore, the quantities can be relatively small, particularly at the high temperatures and pressures. Similarly, the cycle time can be relatively small. With chlorine the preferred amount is between about 0.25-12.0% by weight of the lignocellulose.

Where organic acids are reacted with lignocellulose.

they may be added directly, or if small quantities are used they may be diluted or dissolved with water or an organic solvent such as an alcohol. In general the organic acids are preferably reacted at a pressure between about 200-450 p.s.i. Depending upon the desired product, the organic acids or anhydrides are preferably added in an amount of between 1-25% by weight of the lignocellulose. Table IV sets forth a number of typical comvpositions along with the autoclave conditions under which the materials were processed.

Table IV I Autoclave Reaction Reactant time,

min. Temp, Press,

F. psi.

5% for1nic..-. 20 440 300 5% acetic..... 20 440 300 8% acetic anhy 25 440 300 lus 10% sulfur- 10% butyric plus 10% sulfur 20 440 300 45% butyric plus 2% zinc chloride 20 440 300 10%dbutyric-plus 1% aluminum chlo- 5 400 200 n e I 10% st'earic plus 10% sulfur 20 v 440 300 1% 0xalic 20 440 300 2% oxalic. 20 400 200 5% lactic.-.- 20 440 300 10% phthalic anhy 11 e 20 440 300 65..-. 5%hphtlalic anhydride plus 1% ferric 20 400 200 0 on e All of the precentages given in the above table are by weight of the lignocellulose.

Where organic oils are reacted with lignocellulose in the presence of steam, the pressure required is generally between 300-500 p.s.i. If an acid salt is used in conjunction with the oil, however, much lower pressures can be used. Depending upon the reaction product desired, and the specific oil used, up to 1 part of oil to 1 part of lignocellulose may be added. With drying oils larger quantities may be used than with the non-drying types. The preferred quantity of oil added is between 1-30% based on the weight of the lignocellulose. Table V sets forth the composition, and the autoclave conditions under which a number of reaction products have been prepared.

Table V Autoclave Reaction Ex. Reactant time,

min. Temp, Press,

F. psi.

10% tall Oil 20 440 300 5% tall oil 30 400 400 5% tall oil plus 5% calcium chloride. 20 440 300 5% tall oil plus 5% vinsol plus 3% cal- 20 440 300 cium chloride. 5% tall 011 plus 1% zinc chloride 15 440 300 5% tall oil plus 1% ferric chloride 20 400 200 10% tall oil plus 1% aluminum chl 5 400 200 10% tall oil plus 2% alumi m (10 325 50 10% tall oil plus 1% acctyl ch10 10 375 10% tall oil plus 10% sulfur 20 440 300 5% linseed- 30 440 300 10% linseed 30 460 400 5% linseed plus 25 440 300 10% linseed plus 10% sulfur 20 440 300 10% paraflin oil 30 460 400 10% paraffin oil plus 1% 20 440 300 chloride. 10% paraflin oil plus 0.5% aluminum 20 440 300 chloride.

All of the percentages given in Table V are by weight of the lignocellulose.

Where non-drying types of oils such as parafl'in are used, it is believed that they function to limit to some extent the hydrolytic degradation of the alpha cellulose. The reaction products made with oils appear to be less brittle than when plain lignocellulose is reacted with steam.

The organic oils which may be used as reactants herein are those oils which are unsaturated or which contain a functional group that is capable of reacting with the lignocellulose or with lignocellulose products produced under the high pressure-high temperature conditions of this invention- The natural resins and materials set out herein are intended to include naturally occurring reactants of which rosin, Vinsol, turpentine and the like are examples. In fact, the preferred members of this group are materials produced from pine tree products. Vinsol is identified in my copending application Serial No. 608,-

196, filed September 6, 1956, now Patent No. 2,872,330,

issued February 3, 1959.

In addition to the organic acids and oils, reaction products have been made with lignocellulose and members of the organic classes of alcohols, aldehydes, ketones, phenols, organic bases and nitrogen compounds, monomers and unsaturated compounds, and natural resins and materials. In general these reactants are preferably reacted at pressures of about 300-500 p.s.i. unless an acidic catalyst is used. A number of reactants involving these classes and lignocellulose along with the autoclave conditions are listed in Table VI. All of these reactions were carried out as set forth in Example 1.

Table VI Autoclave Reaction Ex. Reactant time,

min. Temp., Press,

F. p.s.i.

84-.-- 25% ethyl alcohol plus 50 p.s.i. sulfur 10 428 140 dioxide. 85.... 10% isopropyl alcohol 25 440 300 86. 10% isopropyl alcohol plus 0.5% alumi- 20 440 300 nurn chloride. 10% isopropyl alcohol plus 10% sulfur. 20 440 300 10% allyl alcohol plus 10% sulfur 20 440 300 10% ethylene glycol 30 460 400 10% ethylene glycol plus 1% alumi- 20 400 200 num chloride. 20% ethylene glycol plus 1% alumi- 20 400 200 num chloride. 10% glycerine plus 0.5% aluminum 20 400 200 chlori e. 93..-- 10% acetaldehyde 30 440 300 94 ..do 30 460 400 95..-- 10% acetald 20 440 300 96..-- 10% turfural... 2a 440 300 97.... 10% furfural pl sulfur.... 13 440 300 98..-- 5% acetone plus 5 p.s.i. sulfur d1ox1de.. 20 440 300 99..-. 10% mesityl oxide plus 12% sulfur plus 25 440 300 15% Vinsol. 100-.. 10% acetone.-. 30 460 400 101.-. 10% butraldehy e plus 12% sulfur plus 25 440 300 15% Vinsol. 102.-- 10% acetaldehyde plus 12% sulfur plus 25 440 300 15 Vinsol. 103..- glutaraldehyde plus 12% sulfur 25 440 300 plus 15% Vinsol. 104-.- 5% phenol 30 460 400 105..- 5% phenol plus 1% ferric chloride 15 440 300 106... phenol plus 10% sulfur 20 440 300 107--. 10% phenol plus 10% sulfur plus 10% 20 440 300 aniline. 108.-- 5% eresol 25 440 300 109.-- 5% cresol plus 3% ammonium hydrox- 30 440 300 id 110... 5% cresol plus 2% calcium 30 400 400 hydroxide 111-.. 5% cresol plus 3% calcium 20 440 300 chloride. 112... 5% eresol plus 5 p.s.i. sulfur dioxide.... 20 440 300 113.-- 5% eresol plus 10% sulfur 20 440 300 114... 10% cresol plus 10% sulfur plus 10% 20 440 300 ammonium hydroxide. 115..- 10% pentaehlorophenol 20 440 300 116..- 5% aniline 30 440 300 117-.- 30 460 400 118... 20 440 300 119.-. 25 440 300 120.-- 30 460 400 121.. m hydroxide. 30 440 300 122-- o 30 460 400 123.-. 3% formami 30 440 300 124..-- -.do 30 460 400 125-.- 5% dieyandiam 25 440 300 126... 10% dieyandiamide 20 440 300 127-.. 5% melamine 30 440 300 128... 5% urea plus 1% alulr urn chloride..- 10 400 200 129-.- 5% urea plus 5 p.s.i. sulfur dioxide..... 25 440 300 130..- 5% urea plus 5% formaldehyde- 30 460 400 131..- 10% styrene monomer 30 460 400 Autoclave Reaction EX. Beaetant time,

min. Temp, Press.,

1*. p.s.i.

132..- 10% styrene monomer plus 3% calcium 20 440 300 chloride.

133... 10% styrene monomer plus 1% ferric 20 440 300 chloride.

134... 10% styrene monomer plus 0.5% alum- 15 440 300 inum chloride.

135... 10% styrene monomer plus 1.0% alum- 20 400 200 inum chloride.

136... 10% styrene monomer plus 10% sulfur. 20 440 800 137... 10% vinyl acetate monomer 30 460 400 138... 10% 11 inyl acetate monomer plus 10% 20 440 300 s ur.

139.-- 10% dicyclopentadiene 30 460 400 140... 5% dicyclopentadiene plus 3% calcium 20 440 300 chloride.

14.1... 5% dicyclopentadiene plus 1% ferric 15 440 300 chloride.

142... 10% dicyclopeutadiene plus 1% alum- 10 400 200 inum chloride.

143... 20% dicyclopentadiene plus 10% sulfur. 25 440 300 144... 10% allyl chloride plus 10% sulfur plus 20 440 300 5% ammonium hydroxide.

145... 10% wood rosin 30 460 400 146-.- 10% corn starch 30 460 400 117.-. 10% turpentine plus 10% sulfur 25 440 300 All of the percentages given in the above table are by weight of the lignocellulose.

The preferred ranges in which the various classes of reactants illustrated in Table VI are used are set forth below in Table VII. All percentages given are by weight of the lignocellulose.

Table VII Where organic bases are used in the high temperature, high pressure reaction, they appear to function as buffers to some extent. Thus in general somewhat higher pressures or longer reaction times are employed where they are used.

From the examples cited, it is apparent that a large number of different lignocellulose reactions can be carried out with the methods of this invention to produce materials having a wide variety of properties. Thus it is possible to produce reaction products which when molded or pressed or otherwise formed into products such as boards will possess an optimum of certain desired physical properties such as low water absorption, high strength, relatively high plasticity, or. other required properties.

The materials are thus formable at a relatively low temperature in the approximate range of 275-375 F. without the use of excessive pressures. The temperature at which the products are formed is not critical since boards can easily be made at about 400 F. or higher if desired. The ability to form products at lower temperature is an important property since many of the synthetic thermoplastic resins formable at this temperature can thus be blended With the modified lignocellulose, if it is desired to further vary the physical properties of the product.

Formed products can be produced over a wide density range such as with a specific gravity of from approximately 0.5-1.5 depending upon the temperature and pressure used. The pressure utilized can vary from about 25-5000 p.s.i. depending upon the molding temperature and the final product density desired. In general, the lower pressures are used at the higher temperatures. Where boards or preforms are produced the pressure is generally between about 25-800 p.s.i., and the tempera- 9 ture between about 300-400 F. If the materials are molded the higher pressures are used and the temperature preferably between about 275-375 F.

Where boards or preforms are made the particle size of the composition of this invention is preferably between /4 inch-100 mesh as measured on standard screens. The especially preferred particle size is between 20-50 mesh. The press time is only sufiicient to cause the particles to coalesce and bond to each other and to reach the desired board density. The time will, of course, vary with the applied pressure, press temperature and with the material used as well as the thickness of the board. In general the press time is between about 0.220 minutes. A /4 inch thick board can ordinarily be made in 6-8 minutes at a temperature of 350 F. and under 100 p.s.i. pressure.

Where the reaction products of this invention are molded, the product is preferably removed from the reaction vessel and then ground to a powder that is preferably not over about 50 mesh in size. The finely divided moldable material is heated to a temperature just sufficient to flow and fill the mold under the pressure used. The molding time is only sufficient to cause the moldable material to fill the mold and set, and will vary depending upon the type of mold being used, the temperature, the nature of the moldable material and similar factors. In general, the molding time will vary between about 02-15 minutes.

Having described my invention as related to the embodiments set out herein, it is my intention that the in-.

vention be not limited by any of the details of description unless otherwise specified but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. The method of making a moldable lignocellulose product consisting essentially of: intimately mixing particles of lignocellulose and about 0.130.0% by weight of the lignocellulose of an acid of the class consisting of phosphoric, hydrochloric, sulfuric, nitric, formic, acetic, butyric, stearic, oxalic and lactic acids, acetic anhydride and phthalic anhydride; and heating the resulting mixture in the presence of moisture for about 4-60 minutes at a temperature of about 275-475 F. and a confined pressure of about 550 pounds per square inch gauge to combine chemically said lignocellulose and acid.

2. A moldable product prepared by the method of claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 2,156,160 Olsen Apr. 25, 193 2,319,182 Vander Pyl May 11, 1943 2,402,554 Irvine et al. June 25, 1946 2,639,994 Wilson May 26, 1953 2,676,108 Fuller et al. Apr. 24, 1954 2,685,529 Lighthall et a] Aug. 3, 1954 2,692,206 Othmer et al Oct. 19, 1954 2,779,683 Gill Jan. 29, 1957 2,926,114 Grangaard et al Feb. 23, 1960 FOREIGN PATENTS 497,477 Great Britain Dec. 16, 1938 524,056 Great Britain July 29, 1940 854,751 France Apr. 24, 1940 

1. THE METHOD OF MAKING A MOLDABLE LIGNOCELLOSE PRODUCT CONSISTING ESSENTIALLY OF: INTIMATELY MIXING PARTICLES OF LIGNOCLLLOSE AND ABOUT 0.1-30.0% OF WEIGHT OF THE LIGNOCELLULOSE OF AN ACID OF THE CONSISTING OF PHOSPHORIC, HYDROCHLORIDE, SULFURIC, NITRIC, FORMIC, ACETIC BUTYRIC, STEARIC, OXALIC AND LACTIC ACIDS, ACETIC ANYHDRIDE AND PHTHALIC ANHYDRIDE; AND HEATING THE RESULTING MIXTURE IN THE PRESSENCE OF MOISTURE FOR ABOUT 4-60 MINUTES AND A TEMPERATURE OF ABOUT 275-475* F. AND A CONFINED PRESSURE OF ABOUT 30-550 POUNDS PER SQUARE INCH GAUGE TO COMBINED CHEMICALLY SAID LIGNOCELLULOSE AND ACID 